Author's note: these pages were written some years ago. I am not planning to update them. For a more current coverage, see the Palaeos website (to which many links on these pages point to anyway. More info here

Family Parasuchidae

(= Phytosauridae)

The Phytosaurs (this unfortunate name means "plant lizards", because
it was originally mistakenly believed that petrified.mud fillings in the
jaw of the first specimen found were herbivore teeth) were crocodile-like
semi-aquatic thecodonts that suddenly appeared and became very abundant
during the latter part of the Triassic
period.

They are more appropriately known by the later (but less widely used)
name Parasuchia ("alongside the crocodiles"), as they resembled crocodiles
to a remarkable degree in size, appearance, and life-style. This
is an amazing illustration of convergent or parallel evolution. Phytosaurs
were in a sense "crocodile uncles", since both Phytosaurs and proto-crocodiles
shared a common ancestor in early Pseudosuchian thecodonts. But true
crocodiles were only able to evolve after phytosaurs became extinct at
the end of the Triassic.

The differences between phytosaurs and crocodiles are minor. The
most obvious differences between phytosaurs and crocodiles are in the position
of the nostrils. Phytosaurs had nostrils placed near or above the
level of the eyes. Crocodiles have nostrils placed far forward at
the tip of the snout. Another difference is in the palate (roof of
the mouth). True crocodiles have a secondary palate that enables
them to breathe when partially submerged, even though the mouth is full
of water. Phytosaurs lacked this adaptation, and used the nostrils
on top of the head in order to swallow air while underwater. Phytosaur
limbs were also somewhat more primitive in structure than those of crocodiles.
Fossil footprints indicate however that phytosaurs could move in a semi-erect
stance on land and did not drag their tails as modern crocodiles do.

Phytosaurs were if anything even better armoured than crocs, with the
throat and back of the animal being are protected by heavy armoured scutes,
and the belly reinforced with a dense ararngement of abdominal ribs (see
illustration below).

Phytosaurs are divided into two subfamilies (recently sometimes considered
distinct families): the Mystriosuchinae and the Angistorhininae
(= Rutiodontidae).

The Mystriosuchinae represent the more primitive group. They tend
to have gavial-like skulls (e.g. Mystriosuchus, Parasuchus) with
a long, slender snout tipped with a pronounced tusked "hook," and jaws
lined with uniform conical teeth. These were clearly fish eaters.

The Angistorhininae were more heavily built with crocodile- or alligator-like
skulls (e.g Nicrosaurus, Rutiodon) characterised by a shorter, wider,
deeper snout, and jaws equipped with serrated blade-like fangs and more
cylindrical crushing-type teeth. These clearly fed on large animals,
specifically other tetrapods.

However the situition is not so clear cut, as some Mystriosuchines had
Angistorhininae characteristics and some Angistorhinines had Mystriosuchine
characters - indicating the two morphotypes evolved independently in both
lineages

Parasuchidae (=Phytosauridae)

lifestyle: large to very large semi-aquatic carnivores, equivalent
to modern-day crocodile
environment: freshwater rivers, lakes, and swamps
food: fish and smaller tetrapods
enemies: no animal would be stupid enough to take on a large
adult phytosaur
size: from 2 to 8 or even 12 meters (average 3 to 6 meters)
probable ancestor: unspecified early Pseudosuchian
known time range:Late Carnian
to Rhaetianknown distribution: Europe, India, North Africa and North America
status:monophyletic

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